1. Field of the Invention
The present invention relates to a speaker and a portable information terminal, and more particularly, to a speaker having a speaker unit and a box, and a portable information terminal including the same.
2. Description of the Related Art
A speaker is mounted in a portable information terminal such as a mobile phone, smartphone, PDA (Personal Digital Assistants), game machine, or personal computer. Recently, a high sound quality is required in the speaker mounted in the portable information terminal.
When a sound produced from a rear surface of a diaphragm of the speaker comes around to a front surface, a sound produced from the front surface and the sound produced from the rear surface interfere with each other and negated, so that a sound quality is lowered. Since the interference is great in a region having a low frequency, the sound quality is lowered in a low sound especially. As a method to prevent the interference of the sound produced from the rear surface of the diaphragm with the sound produced from the front surface thereof, the rear surface of the diaphragm is hermetically sealed to block out the sound produced from the rear surface of the diaphragm.
Meanwhile, when a volume of a space arranged on the rear surface of the diaphragm is small, a vibration of the diaphragm is prevented due to air resistance in the space. When the rear surface of the diaphragm is simply hermetically sealed as described above, the volume of the space arranged on the rear surface of the diaphragm cannot be ensured, so that the vibration of the diaphragm is prevented due to the air resistance in the space. Therefore, the sound quality is lowered.
Therefore, there is a method in which to increase the volume of the space arranged on the rear surface of the diaphragm while preventing the sound interference, the speaker unit is arranged in a box having the space arranged on the rear surface of the diaphragm, and the box blocks out the sound produced from the rear surface of the diaphragm.
In this case, the speaker unit having the diaphragm, a voice coil, a magnet, and a frame is mounted in the box. In this state, a lead connected to the voice coil is connected to a wire led out of the frame. This wire is routed in the box, and led out of the box through a through hole provided in the box.
Various configurations are proposed for a terminal of the speaker unit. For example, Japanese Patent Laying-Open No. 2002-291094 discloses a speaker mount structure having a terminal pin to which an end of a lead extending from the voice coil is fixed. According to this speaker mount structure, the terminal pin is connected to a conductive section (conductive pattern) of a substrate with soldering under the condition that it is inserted into a pin insert hole, and the terminal pin and the conductive section are electrically connected.
In addition, Japanese Patent Laying-Open No. 2009-278213 discloses an electroacoustic transducer in which a lead led out of the voice coil is connected to an external connection terminal with soldering. According to this electroacoustic transducer, the external connection terminal is formed on a resin insulator fixed to a bottom plate of a frame by insert molding, and it has a fixed section to be buried in the resin, and a spring piece having a cantilever shape extended obliquely downward from the fixed section.
According to the speaker having the speaker unit mounted in the box, in some cases, a wire connected to the speaker unit is led out of the box through a hole provided in the box. In this case, since it is necessary to hermetically seal the hole with a bonding agent under the condition that the wire is led out, the problem is that workability is not good. In addition, when an amount of the bonding agent is small at the time of hermetically sealing the hole with the bonding agent, the sealing is likely to be insufficient, and the problem is that the sound quality becomes unstable due to sound interference. Meanwhile, when the amount of the bonding agent is excessive, the sound quality becomes unstable because a volume ratio of the bonding agent increases in the box.
In addition, according to the speaker having the speaker unit mounted in the box, it is necessary to perform a routing operation for the wire in the box. The routing operation for the wire needs many processes, so that the number of processes increase. That is, the problem is that the workability is not good. In addition, when the routed wire comes into contact with the speaker unit and the box, an abnormal sound is generated. Therefore, the problem is that the sound quality becomes unstable. In addition, hermetically sealed volume in the box decreases due to the volume of the routed wire, so that a sound pressure deteriorates. Thus, the problem is that the sound quality becomes unstable.
In addition, according to the speaker having the speaker unit mounted in the box, in some cases, a terminal provided in the box is connected to the wire in the box, instead of leading out the wire from the box. In this case, it is necessary to connect both ends of the wire. Since the operation to connect the wire needs many processes, the number of the processes increases because the both ends of the wire are connected. Thus, the problem is that the workability is not good.
When the speaker unit and the box are connected with the wire, the above problems arise, so that it is considered that the speaker unit and the box are directly connected without using the wire. In this case, it is necessary to align a terminal of the speaker with a terminal of the box, but the problem is that it is difficult to align the positions because dimensional precision of each component is limited. Since it is difficult to align the positions when the speaker unit and the box are directly connected, the problem is that the workability is not good. Therefore, it is difficult to directly connect the speaker unit and the box without using the wire.
Thus, it is considered that the speaker unit and the box are connected with the terminal pin instead of using the wire as disclosed in the Japanese Patent Laying-Open No. 2002-291094. However, the speaker mount structure in this document is not a structure in which the speaker unit is arranged in the box, so that the pin terminal becomes a hindrance in mounting the speaker. Therefore, the problem is that the workability is not good in this case also. In addition, since the pin terminal is provided outside the speaker, a range occupied by the speaker increases. Thus, the problem is that the space cannot be saved.
Furthermore, it is considered that instead of using the wire, the speaker unit and the box are connected with the external connection terminal having the spring piece as disclosed in the above Japanese Patent Laying-Open No. 2009-278213. However, the external connection terminal having the spring piece in this document has problems such as a conduction defect caused by the separation of a contact point of the spring piece due to the vibration, a conduction defect caused by plastic deformation of the spring piece, and a conduction defect caused by a stain of the contact point of the spring piece. In addition, the problem is that a mount position shifts due to a reaction force of the spring piece.
Therefore, a mechanism or an operation to hold a position of the spring piece so as to prevent the above conduction defect and to prevent the mount position from shifting is needed in mounting the speaker unit in the box. In addition, it is necessary to limit a position of a rear hole of the frame and enlarge an outer diameter of the frame to ensure an area for the spring piece. Thus, the problem is that the space cannot be saved. In addition, the problem is that the workability is not good due to the above operation.